1. Field of the Invention
The invention relates to a measuring-point bolt for the temporary attachment of measuring devices to both ends of the bolt.
2. Discussion of Background Information
The accuracy of the dimensions of certain objects (e.g. aircraft) is monitored during and after assembly, after a certain number of hours of operation, or following abnormal stress. For this purpose, measurement points are provided (e.g. on aircraft) from which the dimensional accuracy can be checked using measuring devices.
Such a measuring points are formed by a bolt which is connected permanently to the wall of the aircraft and which has two free ends, i.e., one on either side of the wall. When required, measurement devices are located temporarily on the ends of these bolts.
Measuring-point bolts of the following type e.g., AIRBUS standard NSA9501, have been in use. FIG. 2 illustrates such a device. The measuring-point bolt 1′ has a flange 2′ for attaching the bolt 1′ to the wall of the aircraft. In the direction of the bolt axis, there is provided an interior hole 5′ for receiving a spiral pressure spring 6′. At bolt end A′ there is arranged a threaded insert 10′ which forms a stop for the pressure spring 6′. End A′ also has a bore 3′ for receiving a pin which is connected with a first measuring device.
When the measuring device pin is inserted into the receiving bore 3′, an element 9′ which is movably located in the bore 3′, which is connected with the pressure spring 6′ and which serves to prevent entry of undesirable foreign particles, is pressed in direction D against the biasing force of the pressure spring 6′.
When the measuring device pin is removed from the interior bore 3′, the pressure spring 6′ pushes the element 9 back in the direction of the opening of the interior bore 3′, i.e., opposite direction D.
The other bolt end B′ of the bolt 1′ has a cylindrical outer-shaft area 4′. This end B′ is designed to be connected to a hollow bolt of a second measuring device (not shown). In this arrangement, the hollow bolt can be pushed onto the other end B′.
The end B′ includes a closed base 7′, which passes over into a wall of the hollow bolt. The closed base 7′ ensures that when the measuring-point bolt is installed in the wall of aircraft, no equalization of air pressure can take place between the interior bore 5′ and an area outside the bolt-end B′ (to the left of the imaginary wall of the aircraft).
High tolerance demands are increasingly being made on such measuring-point bolts. However, known measuring-point bolt are no longer able to fulfil these demands. This is because they utilize a threaded insert 10′ (with the screw-in area 10″) which is inserted relatively “inaccurately” into the bolt end A′.